RE: MilCAN processors

Thanks Kees,

Interesting undocumented feature.  I wonder if the PIC ECAN will do that? 
I'll do some research and report back.

I do agree with Wim that an ERROR FRAME should be allowed but 
re-transmissions should be prevented for MilCAN.

John Dammeyer


"ELS! The Solution"
Automation Artisans Inc.
http://www.autoartisans.com/ELS/
Ph. 1 250 544 4950


> -----Original Message-----
> From: [email protected]
> [mailto:[email protected]] On
> Behalf Of [email protected]
> Sent: Thursday, December 20, 2012 12:26 AM
> To: [email protected]
> Subject: RE: [CANLIST] MilCAN processors
>
>
> Hi John, Wim,
>
> In my opinion error frames should be produced also in MILCAN, because
> everyone has to know that the message is invalid. The CAN-controllers
> should have the possibility to do a so-called "single-shot"
> transmission. The good-old SJA1000 controller can do that and I think
> also more modern CAN controllers. If you set TX request and Tx abort
> simultaniously a single-shot transmission is performed.
>
> Kees
>
> Stremerch, Wim schreef op 20.12.2012 07:51:
> > Message
> >
> > Hi John,
> >
> > Error frames are allowed on the bus, but if a controller sees an
> > error
> > frame it should not retransmit the message.
> >
> > We use a controller that supports TTCAN. In this mode it will not
> > retransmit the message when an error frame is received.
> >
> > Best regards,
> >
> > Wim Stremerch
> >
> > FROM: [email protected]
> > [mailto:[email protected]] ON BEHALF OF
> > John
> > Dammeyer
> > SENT: donderdag 20 december 2012 1:08
> > TO: 'CANLIST'
> > SUBJECT: [CANLIST] MilCAN processors
> >
> > Hi Everyone,
> >
> > One of the MilCAN specifications is that a node is not allowed to
> > issue an error frame to get a message retransmitted. As I understand
> > it the designers of MilCAN wanted to insure that the Sync Flag
> > Message
> > always showed up at exactly the same time. Since the number of
> > replies
> > in each sync slot are restricted only a large burst of higher
> > priority
> > messages could thwart the sync flag. And an error burst that caused
> > retries.
> >
> > For example. Imagine there is time for 20 messages between SYNC
> > FLAGs.
> > The system designer has one SYNC FLAG where there are 18 replies
> > leaving room for two ASYNC messages. Say 4 of the replies are
> > corrupted by a noise burst during the CRC. The retries would now
> > extend past the time point for a new SYNC FLAG and potentially it
> > would be shifted or delayed. Plus old data would show up in the next
> > SYNC Slot.
> >
> > The trouble is, there are very few CAN devices out there that can
> > have
> > the ERROR frame turned off. Yes, the node can go to listen mode but
> > then all messages get through including ones with invalid CRCs.
> >
> > Has anyone run into a processor family where this is possible? Am I
> > misinterpreting the MilCAN spec?
> >
> > Best Regards,
> >
> > John Dammeyer
> >
> > "ELS! The Solution"
> > Automation Artisans Inc.
> > http://www.autoartisans.com/ELS/ [1]
> > Ph. 1 250 544 4950
> >
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